• ICSI is the injection of a single sperm into a mature oocyte (eggs) in the laboratory using micromanipulation techniques.
  • ICSI provides a means of overcoming the problems of IVF in horses.
  • Clinical use of this technology provides a means of producing foals from sub fertile mares and stallions and assists in rescuing the fertility of aged mares and stallions.
  • ICSI employs ovum pick up (OPU) of mature oocytes (eggs) from the donor mares by follicle aspiration.
  • OPU can also harvest immature oocytes and those eggs can be cultured in the lab until they become mature oocytes (metaphase ll).
  • The mature oocytes are then injected with a single sperm cell using micromanipulation techniques.
  • The resulting fertilized egg is cultured in the lab until it reaches the expanded blastocyst stage (day 6,7,8, or 9)
  • The embryo can then be transferred non-surgically to a recipient mare (preferably 5 days post ovulation) or frozen for use later.
  • The loss of fertility associated with aged oocytes can be overcome with ICSI.

Chad Bushaw

2012 #1 Non-Pro Rider, #3 Top Owner - Crown Ranch

I think the more people know and understand about the ICSI process, the more they will realize that it actually does work and it isn't as invasive to mares as it once was......The reality is that its a game-changer-- Because now we can breed to stallions that have frozen semen stored. There's a lot of these great horses that we are now able to greatly extend their production years as the technology keeps evolving.


The intracytoplasmic sperm injection (ICSI) program is offered at Texas A&M as a means of establishing pregnancies from oocytes (eggs) recovered from donor mares. Using ICSI, oocytes are injected with individual sperm from a donor stallion, and the resulting embryos are allowed to develop in the laboratory for approximately one week. Developed embryos are then shipped to a private embryo transfer facility for transfer to a recipient mare, as for standard embryo transfer.

This advanced reproductive technology is appropriate for mares that are unable to become pregnant themselves (i.e., mares with chronic uterine disease, cervical lacerations, or other damage to the reproductive tract that prohibit the mare from conceiving or supporting an embryo in the uterus for any length of time). The procedure can also be attempted when pregnancies are sought from limited sperm supplies.

The procedure should only be used on mares that are not suitable candidates for routine embryo transfer (i.e., mares in which viable embryos are seldom recovered from standard uterine flushing), or, if done to obtain foals from a given stallion, for sperm that cannot be utilized effectively with standard insemination techniques. Because of the expense of the technology involved and the amount of labor associated with ICSI, foals produced from this program should be valuable enough to justify the increased effort and expense to produce offspring. Before participating in the ICSI program, it is important for each owner/lessee to know the regulations of their breed registry regarding the possibility of registering any resulting foals.


Intracytoplasmic sperm injection is a recently developed technique in which oocytes (eggs) of a valuable broodmare (donor mare) are fertilized in the laboratory. The oocytes are recovered from the mare's ovarian follicles, and then cultured to induce maturation, mimicking the developmental changes that would occur in an oocyte during the day or so immediately before ovulation. This maturation process generally takes 12 to 30 hours, depending upon the stage of maturation of the recovered oocytes.

Matured oocytes are injected with individual sperm from the desired stallion. For this procedure, one sperm is injected into the cytoplasm of each oocyte under a high-power microscope. The resulting fertilized oocytes are cultured in the laboratory for 7 to 10 days, to allow development into blastocysts, that is, embryos suitable for transfer to a recipient mare. Embryos will be shipped to a private embryo transfer facility for transfer to recipient mares.


This program (fertilization and embryo development in the laboratory) has some benefits over oocyte transfer (surgical transfer of matured oocytes to the oviducts of inseminated recipient mares). The major benefit is that it avoids the need for surgery on the recipient mare, as embryos develop in the laboratory to the stage that they may be transferred to recipients by standard embryo transfer. Because of this, when multiple oocytes are recovered, all oocytes that form embryos may be transferred to separate recipient mares, and thus have the potential to produce a foal. In addition, the ICSI program can utilize equally frozen, fresh, or cooled, transported semen, and sperm of low numbers or low quality.




Elaine M. Carnevale, DVM, PhD

Associate Professor
Department of Biomedical Sciences
Animal Reproduction and Biotechnology Laboratory
Colorado State University
Fort Collins, CO 80523

Office: W131 ARBL Building, Foothills Campus
Phone: 970-491-8626
Fax: 970-491-3557
Email: Elaine.Carnevale@ColoState.edu

Animal Reproduction and Biotechnology Laboratory

PhD, University of Wisconsin-Madison
DVM, Colorado State University
MS, Colorado State University
BS, Colorado State University

EM Carnevale PubMed